Three lines of investigation are proposed: (1) Studies of control of skin blood flow and sweating plus their interrelationships in man. Skin temperature is tightly controlled and driven in various temporal patterns to separate quantitative roles of skin and internal temperatures on measured variables - particularly contributions of released vasoconstrictor tone vs. active vasodilation in skin. (2) Analogous studies on primates wherein skin and central body temperatures are separately controlled. (3) Studies on man and primates to define patterns of regional blood flow and quantitative significance of regional vasoconstriction in response to thermal stimuli and reduced central venous vs. arterial pressure changes.